Backed out changeset 109e5bafd7a3 (bug 1398623) for asserting during a11y's e.g. accessible/tests/mochitest/states/test_expandable.xul. r=backout

layout/xul/nsSprocketLayout.cpp

@@ -736,6 +736,7 @@ nsSprocketLayout::PopulateBoxSizes(nsIFrame* aBox, nsBoxLayoutState& aState, nsB
     nsSize pref(0,0);
     nsSize minSize(0,0);
     nsSize maxSize(NS_INTRINSICSIZE,NS_INTRINSICSIZE);
+    nscoord ascent = 0;
     bool collapsed = child->IsXULCollapsed();
 
     if (!collapsed) {
@@ -746,6 +747,10 @@ nsSprocketLayout::PopulateBoxSizes(nsIFrame* aBox, nsBoxLayoutState& aState, nsB
       pref = child->GetXULPrefSize(aState);
       minSize = child->GetXULMinSize(aState);
       maxSize = nsBox::BoundsCheckMinMax(minSize, child->GetXULMaxSize(aState));
+      ascent = child->GetXULBoxAscent(aState);
+      nsMargin margin;
+      child->GetXULMargin(margin);
+      ascent += margin.top;
     //}
 
       pref = nsBox::BoundsCheck(minSize, pref, maxSize);